Control of the Mode Selectivity (Ene Reaction versus [2 + 2] Cycloaddition) in the Photooxygenation of Ene Carbamates: Directing Effect of an Alkenylic Nitrogen Functionality
作者:Waldemar Adam、Sara G. Bosio、Nicholas J. Turro
DOI:10.1021/ja028407m
日期:2002.11.1
The geometry of the double bond in oxazolidinone-substituted ene carbamates controls the mode selectivity (ene reaction versus [2+2] cycloaddition) of singlet oxygen through stereoelectronic effects, whereas the chiral auxiliary provides high diastereoselectivity through steric shielding.
Chiral-Auxiliary-Controlled Diastereoselectivity in the Epoxidation of Enecarbamates with DMD and <i>m</i>CPBA
作者:Waldemar Adam、Sara G. Bosio、Barbara T. Wolff
DOI:10.1021/ol0273194
日期:2003.3.1
text] Chiral oxazolidinone-substituted enecarbamates 1 are epoxidized in a diastereoselectivity up to 93:7 for both DMD and mCPBA. The diastereofacial differentiation depends on the steric interaction between the R(1) substituent on the oxazolidinone ring and the incoming electrophile. The stereochemical course of epoxidation was assessed by chemical correlation with the known optically active diols
Combined Theoretical and Experimental Studies Unravel Multiple Pathways to Convergent Asymmetric Hydrogenation of Enamides
作者:Jianping Yang、Luca Massaro、Suppachai Krajangsri、Thishana Singh、Hao Su、Emanuele Silvi、Sudipta Ponra、Lars Eriksson、Mårten S. G. Ahlquist、Pher G. Andersson
DOI:10.1021/jacs.1c09573
日期:2021.12.29
We present a highly efficient convergent asymmetric hydrogenation of E/Z mixtures of enamides catalyzed by N,P–iridium complexes supported by mechanistic studies. It was found that reduction of the olefinic isomers (E and Z geometries) produces chiral amides with the same absolute configuration (enantioconvergent hydrogenation). This allowed the hydrogenation of a wide range of E/Z mixtures of trisubstituted
Enecarbamates as Selective Substrates in Oxidations: Chiral-Auxiliary-Controlled Mode Selectivity and Diastereoselectivity in the [2+2] Cycloaddition and Ene Reaction of Singlet Oxygen and in the Epoxidation by DMD and <i>m</i>CPBA
作者:Waldemar Adam、Sara G. Bosio、Nicholas J. Turro、Barbara T. Wolff
DOI:10.1021/jo035745c
日期:2004.3.1
The stereochemical course of the oxidation of chiral oxazolidinone-substituted enecarbamates has been studied for singletoxygen (1O2), dimethyldioxirane (DMD), and m-chloroperbenzoic acid (mCPBA) by examining of the special structural and stereoelectronic features of the enecarbamates. Valuable mechanistic insight into these selective oxidations is gained. Whereas the R1 substituent on the chiral
手性恶唑烷酮取代enecarbamates氧化的立体化学过程已经研究了单重态氧(1 Ò 2),二甲基二(DMD),和中号氯过苯甲酸(米通过的enecarbamates的特殊的结构和立体电子特征检查CPBA) 。获得了对这些选择性氧化的有价值的机理见解。而手性助剂上的R 1取代基负责双键的空间屏蔽,并决定π面非对映选择性的感觉,Z / E构型等结构特征和R 2的性质双键上的基团负责非对映选择性的程度。在1 O 2的情况下,通过乙烯基氮官能团进行的立体电子控制可控制模式选择性(烯反应与[2 + 2]环加成反应)。